Methods for selective removal of contact oxides

Abstract

A method for cleaning contacts on a substrate incorporates ion control to selectively remove oxides. The method includes exposing the substrate to ions of an inert gas, supplying a first RF frequency of a first bias power supply to a substrate support, supplying a second RF frequency of a second bias power supply to a substrate support, and adjusting a first power level of the first RF frequency and a second power level of the second RF frequency to selectively remove oxide from at least one contact on the substrate while inhibiting sputtering of polymer material wherein the oxide removal is selective over removal of polymer material surrounding the at least one contact.

The invention claimed is: 
     
       1. A method for cleaning contacts on a substrate, comprising:
 exposing the substrate to ions of an inert gas; 
 supplying a first RF frequency of a first bias power supply to a substrate support, wherein the first RF frequency controls ion energy of the ions of the inert gas; 
 supplying a second RF frequency of a second bias power supply to a substrate support, wherein the second RF frequency controls ion density of the ions of the inert gas and is a higher frequency than the first RF frequency; and 
 adjusting a first power level of the first RF frequency and a second power level of the second RF frequency to selectively remove oxide from at least one contact on the substrate while inhibiting sputtering of polymer material and re-contamination of the at least one contact with the polymer material, wherein the oxide removal is selective over removal of the polymer material surrounding the at least one contact by altering the first power level of the first RF frequency to increase ion energy and wherein a rate of oxide removal on the at least one contact is increased by altering the second power level of the second RE frequency to increase ion density. 
 
     
     
       2. The method of  claim 1 , further comprising:
 decreasing an inert gas flow rate during oxide removal to increase the ion energy. 
 
     
     
       3. The method of  claim 2 , wherein the inert gas flow rate is greater than zero to approximately 50 sccm. 
     
     
       4. The method of  claim 1 , further comprising:
 reducing a temperature of the substrate to approximately −20 degrees Celsius to approximately 60 degrees Celsius during oxide removal to further inhibit sputtering of polymer material. 
 
     
     
       5. The method of  claim 4 , wherein the temperature is approximately −20 degrees Celsius. 
     
     
       6. The method of  claim 1 , further comprising:
 maintaining a process pressure of approximately 0.7 mTorr to approximately 20 mTorr during oxide removal. 
 
     
     
       7. The method of  claim 1 , wherein the first RF frequency is approximately 400 kHz to approximately 15 MHz and the second RF frequency is approximately 40 MHz to approximately 110 MHz. 
     
     
       8. The method of  claim 7 , wherein the first RF frequency is approximately 13.56 MHz and the second RF frequency is approximately 60 MHz. 
     
     
       9. The method of  claim 1 , wherein a selectivity ratio of removal of oxide to removal of polymer material is at least 2:1. 
     
     
       10. The method of  claim 1 , wherein the polymer material is polyimide material or polybenzoxazole material. 
     
     
       11. The method of  claim 1 , wherein the contact is aluminum material and oxide is aluminum oxide. 
     
     
       12. The method of  claim 1 , wherein the method is performed in a wafer level packaging process. 
     
     
       13. The method of  claim 1 , wherein the inert gas is argon. 
     
     
       14. The method of  claim 1 , wherein the first power level is greater than zero to approximately 2000 W and the second power level is greater than zero to approximately 2000 W. 
     
     
       15. A method for cleaning contacts on a substrate, comprising:
 exposing the substrate to ions from argon gas with a gas flow rate of greater than zero to approximately 50 sccm, wherein decreasing the gas flow rate increases ion energy; 
 supplying a first RF frequency of 13.56 MHz from a first bias power supply to a substrate support, wherein the first RF frequency controls ion energy of the ions of the argon gas; 
 supplying a second RF frequency of 60 MHz from a second bias power supply to a substrate support, wherein the second RF frequency controls ion density of the ions of the argon gas; and 
 adjusting a first power level of the first RF frequency and a second power level of the second RF frequency to selectively remove aluminum oxide from at least one contact of aluminum material on the substrate while inhibiting sputtering of polymer material and re-contamination of the at least one contact with the polymer material, wherein the aluminum oxide removal is selective over removal of the polymer material surrounding the at least one contact by altering the first power level of the first RF frequency to increase ion energy and wherein a rate of oxide removal on the at least one contact is increased by altering the second power level of the second RF frequency to increase ion density. 
 
     
     
       16. The method of  claim 15 , further comprising:
 reducing a temperature of the substrate during oxide removal to further inhibit sputtering of polymer material during oxide removal, wherein the temperature is approximately −20 degrees Celsius. 
 
     
     
       17. The method of  claim 15 , further comprising:
 maintaining a process pressure of approximately 0.7 mTorr to approximately 20 mTorr during oxide removal. 
 
     
     
       18. The method of  claim 15 , wherein a selectivity ratio of removal of aluminum oxide to removal of polymer material is at least 2:1. 
     
     
       19. A non-transitory, computer readable medium having instructions stored thereon that, when executed, cause a method for cleaning contacts on a substrate, the method comprising:
 exposing the substrate to ions of an inert gas; 
 supplying a first RF frequency of a first bias power supply to a substrate support, wherein the first RF frequency controls ion energy of the ions of the inert gas; 
 supplying a second RF frequency of a second bias power supply to a substrate support, wherein the second RF frequency controls ion density of the ions of the inert gas and is a higher frequency than the first RF frequency; and 
 adjusting a first power level of the first RF frequency and a second power level of the second RF frequency to selectively remove oxide from at least one contact on the substrate while inhibiting sputtering of polymer material and re-contamination of the at least one contact with the polymer material, wherein the oxide removal is selective over removal of the polymer material surrounding the at least one contact by altering the first power level of the first RF frequency to increase ion energy and wherein a rate of oxide removal on the at least one contact is increased by altering the second power level of the second RF frequency to increase ion density. 
 
     
     
       20. The non-transitory, computer readable medium of  claim 19 , the method further comprising:
 reducing a temperature of the substrate during oxide removal to further inhibit sputtering of polymer material, wherein the temperature is approximately −20 degrees Celsius to approximately 60 degrees Celsius; and 
 maintaining a process pressure of approximately 0.7 mTorr to approximately 20 mTorr during oxide removal.